MONDAY, Sept. 19, 2016 -- The U.S. Food and Drug Administration on Monday granted preliminary approval to the first drug for a rare form of muscular dystrophy.

Exondys 51 (eteplirsen) was granted accelerated approval to treat Duchenne muscular dystrophy, a genetic disorder that progressively weakens the muscular systems of its victims. Most are in a wheelchair by their teens and do not survive past their 20s or 30s.

"Patients with a particular type of Duchenne muscular dystrophy will now have access to an approved treatment for this rare and devastating disease," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in an agency news release.

"In rare diseases, new drug development is especially challenging, due to the small numbers of people affected by each disease and the lack of medical understanding of many disorders," Woodcock said.

"Accelerated approval makes this drug available to patients based on initial data, but we eagerly await learning more about the efficacy [effectiveness] of this drug through a confirmatory clinical trial that the [drug's maker] must conduct after approval," Woodcock added.

The FDA gave its accelerated approval even though an agency advisory panel had recommended against the drug, saying there was little evidence that it benefited patients. That advisory vote was met with significant pushback from patients' families, some physicians and politicians, the Associated Press reported.

Under the accelerated approval provision, the FDA is requiring the maker of Exondys 51 -- Sarepta Therapeutics of Cambridge, Mass. -- to conduct a clinical trial to confirm that the drug helps patients.

Duchenne is the most common form of muscular dystrophy. The disease occurs when the body lacks a protein, called dystrophin, that helps keep muscle cells intact.

Exondys 51, which is injected, is specifically used for the treatment of patients who have a confirmed mutation in the gene that produces dystrophin, the FDA said.

Essentially, the drug helps cells "skip" over the faulty section of genetic coding and allows the production of a form of the dystrophin protein, according to Sarepta Therapeutics.

Exondys 51 was placed on a fast-track approval, which speeds up the review of drugs that are intended to treat serious or life-threatening conditions or have the potential to address an unmet medical need. This approval can be based on research that shows there is a reasonable likelihood that the drug will benefit patients, the FDA said.

Exondys 51 was also given an "orphan drug" designation, which provides certain financial incentives to drug makers to encourage the development of drugs for rare diseases.

The accelerated approval was based on findings that the drug helped increase skeletal muscle in some patients, the FDA said.

Commonly reported side effects among those taking Exondys 51 included balance disorder and vomiting. The FDA said its decision to grant preliminary approval to the drug takes into account that Duchenne is a life-threatening and debilitating disease affecting children.

Disease symptoms usually develop early in life, between the ages of 3 and 5, and become more severe with age. People lose the ability to perform normal daily tasks without help. Many patients must use a wheelchair by the time they are teenagers. Over time, potentially fatal heart and lung conditions can develop.

Boys develop Duchenne far more often than girls. But, the disease can affect anyone -- even those who don't have a family history of the genetic disorder, the FDA said. Roughly one of every 3,600 male infants worldwide has the disease.